I find it quite puzzling that no build for i386 exists in backports for quite a few dependencies of the meta-package xfce4.

When I try: aptitude -t lenny-backports install xfce4

I get errors saying that dependencies: xfdesktop4, orage, thunar and others can't be satisfied.
Checking in the debian packages website I found out why...there is no build for these packages for i386!, only amd64 and ppc.